NEVER Use a Comma in These Situations

Commas have many, MANY uses, from separating elements in a series to setting off introductory phrases to separating a speaker from their quotation to surrounding nonrestrictive clauses and so much more.

But there are definitely some times when you should NOT use a comma—in fact, using one in any of these six situations would be a grave grammatical mistake.

🚫 Joining Independent Clauses 🚫

An independent clause has a subject and verb, and it can stand on its own as a complete sentence. If you have two independent clauses, you cannot join them together with just a comma. This is called a comma splice, and it is perhaps the cardinal sin of comma usage.

I went to the store. I needed milk and eggs. <—These are both independent clauses. They CANNOT be joined together with just a comma.

I went to the store, I needed milk and eggs. <—THIS IS BAD. This is a comma splice.

To join together two independent clauses with a comma, you can add a coordinating conjunction (one of the FANBOYS words):

I went to the store, for I needed milk and eggs.

Another option is to turn one of the independent clauses into a DEPENDENT clause by adding a subordinating conjunction:

Because I needed milk and eggs, I went to the store.

Your final option is to swap out the comma for a more powerful punctuation mark, like a semicolon or period:

I went to the store; I needed milk and eggs.

I think of independent clauses as being powerful and heavy. Handling two of them at once without any help from coordinating conjunctions or stronger punctuation marks is just too much for our little friend the comma. It’s trying to support two equally proud and defiant clauses, and it will fail without help.

The only exception to this rule is when you have very short clauses that all have the same subject, like the famous quote “I came, I saw, I conquered.”

Comma splices still confusing you? Check out this post for more details and examples!

🚫 Between the Subject and Part of a Compound Predicate 🚫

A compound sentence is made up of two independent clauses, which each have a subject and verb. A compound predicate, however, is made up of one independent clause that has a single subject and two (or more) verbs.

Glinda told Dorothy to follow the yellow brick road and warned her to watch out for the Wicked Witch of the West.

This sentence has one subject (Glinda) and two predicates (“told Dorothy to follow the yellow brick road” and “warned her to watch out for the Wicked Witch of the West”). You can tell that it’s not a compound sentence because we couldn’t separate it into two sentences that both make sense on their own. “And warned her to watch out for the Wicked Witch of the West” is not a complete sentence—it’s missing its subject (Glinda).

Do not separate the second part of a compound predicate from its subject.

Glinda told Dorothy to follow the yellow brick road, and warned her to watch out for the Wicked Witch of the West.

The comma after “road” separates the subject “Glinda” from the second part of its compound predicate “and warned her.”

If you can’t find the subject after the comma, you may have accidentally stranded it earlier in the sentence!

Dorothy met several friends on her way to the Emerald City, and hoped the Wizard of Oz would help them all.

That second phrase “and hoped the Wizard of Oz would help them all” is not able to stand on its own. It’s missing a subject—WHO hoped? Dorothy hoped. But we stranded the subject (Dorothy) earlier in the sentence by adding a comma, so we need to remove it in order to fix that.

Dorothy met several friends on her way to the Emerald City and hoped the Wizard of Oz would help them all.

Note that you SHOULD use commas to separate the predicates if you have three or more and you need to punctuate them as a series.

Dorothy splashed water on the Wicked Witch of the West, was given the witch’s broomstick by the guards, and took that broomstick back to the Wizard of Oz.

🚫 When Setting Off a Restrictive Appositive 🚫

That’s a lot of big words, so let’s break it down. An appositive is just a word that renames a noun. It appears next to a noun or pronoun and explains or identifies it.

The movie Harry Potter and the Chamber of Secrets will be shown in theaters for a limited time.

In this sentence, “the movie” is a noun, and “Harry Potter and the Chamber of Secrets” is an appositive that renames and identifies it.

A RESTRICTIVE appositive is an appositive that is essential information—the sentence wouldn’t make sense without it. For example, if we took out the appositive in the above sentence, you wouldn’t know WHICH movie was being shown in theaters.

The movie will be shown in theaters for a limited time.

Because we need that information in order to understand the sentence, it’s a restrictive appositive. When it’s restrictive, you should NOT surround it with commas.

The movie, Harry Potter and the Chamber of Secrets, will be shown in theaters for a limited time.

NONrestrictive appositives are NOT essential information:

My favorite movie, Harry Potter and the Chamber of Secrets, will be shown in theaters for a limited time.

I only have one favorite movie, so someone who knows me well might not need the title of the movie in order to understand which one is being shown in theaters. For that reason, it’s a nonrestrictive appositive, and that means we SHOULD surround it with commas.

Basically, if it’s essential information, DON’T cut it off with commas.

🚫 Before an Indirect Quote 🚫

You usually should have a comma between a speaker and their quote, like this:

My boss asked, “Would you mind coming in to work on Saturday?”

However, when it’s an INDIRECT quotation, meaning you’re not repeating the speaker’s exact words, you should NOT set it off with a comma:

My boss asked, whether I could come in on Saturday.

My boss asked whether I could come in on Saturday.

If there aren’t quotation marks, you shouldn’t cut it off with commas!

Learn more about commas and quotes here!

🚫 Before a Quote that’s Integrated Into the Sentence 🚫

If you could remove the quotation marks from a sentence and no one would know that a quote was ever there, then you should not introduce the quote with a comma.

So this sentence would require a comma:

Sherlock Holmes said, “I am a brain, Watson. The rest of me is a mere appendix.”

But this one would not:

Sherlock Holmes said that he is “a brain” and the rest of him is a “mere appendix.”

If we remove those quotation marks, we’d never know they were there in the first place. This sentence makes perfect sense: Sherlock Holmes said that he is a brain and the rest of him is a mere appendix.

With commas, that sentence cannot flow properly and is awkward to read:

Sherlock Holmes said that he is, “a brain,” and the rest of him is a, “mere appendix.”

If you have a verb like “said,” “replied,” or “asked” before the quote, you probably DO need a comma. But if you have a conjunction like “that,” “whether,” or “if” before the quote, you probably DON’T need a comma.

Learn more about commas and quotes here!

🚫 In the Middle of a So . . . That Construction 🚫

When you’re saying that something was so {insert adjective here} that {insert result here}, you should NOT separate those two phrases with a comma.

The snow was so heavy, that I couldn’t get to work.

The snow was so heavy that I couldn’t get to work.

I think people add in the commas because it might feel natural to pause there when saying the sentence out loud, but commas add too much separation—the so and that phrases are closely related, so you don’t want to chop them in half with a comma.

4 Common Comma MISTAKES

What questions do you have about commas? Drop them in the comments!

Sources:

• The Chicago Manual of Style. 17th ed. Chicago, IL: The University of Chicago Press, 2017.
• Einsohn, Amy. The Copyeditor’s Handbook. 3rd ed. Berkeley and Los Angeles, California: Univ of California Pr, 2011.